Known charge generating materials having sensitivity in the near infrared region which can be used in electrophotographic photoreceptors include squarylium pigments, bisazo pigments, and phthalocyanine pigments. Of these materials, oxytitanium phthalocyanine has recently been attracting particular attention because of its high sensitivity, and various species thereof having different crystal forms have hitherto been proposed for use as a charge generating material of electrophotographic photoreceptors. For example, the .alpha.-crystal form is disclosed in JP-A-61-217050; the .beta.-crystal form in JP-A-59-49544; the C-crystal form in JP-A-62-256865; the D-crystal form in JP-A-62-67094; the Y-crystal form in JP-A-64-17066; the .gamma.-crystal form in JP-A-1-299874; and the .omega.-crystal form in JP-A-2-99969, respectively (the term "JP-A" as used herein means an "unexamined published Japanese patent application"). Further, the D-, Y-, and .gamma.-crystals forms are known to have an X-ray diffraction peak at a Bragg angle (2.theta..+-.0.2) of around 27.2.degree..
On the other hand, gallium phthalocyanine (see JP-A-1-221459) and indium phthalocyanine (see JP-A-60-59355 and JP-A-61-124951) were also reported to be effective as a charge generating material for electrophotographic photoreceptors.
Additionally, JP-A-1-142658, JP-A-1-221461, JP-A-2-70763, JP-A-2-170166, JP-A-2-272067, and JP-A-2-280169 proposed use of a crystal of mixed pigments or mere mixture of oxytitanium phthalocyanine and other phthalocyanine as a charge generating material.
However, a crystal of mixed pigments of oxytitanium phthalocyanine and a halogenated gallium phthalocyanine or a halogenated indium phthalocyanine has not yet been reported.
While the above-described known oxytitanium phthalocyanine species and crystals of mixed pigments thereof are useful as a charge generating material, they are still unsatisfactory. For example, the oxytitanium phthalocyanine having the maximum diffraction peak at a Bragg angle (2.theta..+-.0.2.degree.) of 27.3.degree., disclosed in JP-A-62-67094 supra, exhibits very high sensitivity but is still insufficient in stability on repeated use, crystal form stability in a coating composition, and dispersibility in a coating composition. In order to settle these problems, it has been proposed to mix oxytitanium phthalocyanine with a small amount of a substituted phthalocyanine as described, e.g., in JP-A-3-9962, JP-B-55-27583, and JP-B-54-44684 (the term "JP-B" as used herein means an "examined Japanese patent publication"). In this case, however, since a substituted phthalocyanine is markedly different from unsubstituted phthalocyanine in crystal form, mixing them gives rise to another problem, such as reduction in electrophotographic characteristics.